Materials Science Forum Vol. 1022

Abstract: The article addresses the features of rock disintegration based on the principles of selective and preferential destruction in high-frequency cone vibratory crushers with a free-turning inner cone. Based on the common method for determining the ultimate strength of rocks, a method for investigating the process of ore destruction under repeated and versatile influences has been proposed depending on the structure of the crushed material. The results of an experimental research of the destruction of rock samples on a press with limited force are given.

Abstract: Currently, welded heterogeneous structures are widely used in mechanical engineering. The mechanical processing of such complex products is accompanied by a self-oscillating process. For reducing the intensity of vibration, boring bar with an adjustable stress-strain state has to be used. Studies that were carried out by authors made possible to establish the influence of the microstructure of steels after heat treatment and in various stress states on the damping capacity. Εstablished influence allowed to select steel for the manufacture of a boring bar, in the inner cavity of which an expanding cone was installed for creating of a stress-strain state. Subsequent investigations as well made possible to establish the influence of the microstructure and the stress-strain state of the boring bar on the dynamic characteristics of the boring process of the welded structure. Such an approach enables preliminarily estimating the level of vibration amplitude while boring a heterogeneous welded structure, and to provide the specified parameters for the surface roughness of a precision product at the manufacturing stage.

Abstract: The correct selection of technology for processing potash ore depends on its mineralogical composition, the natural size and shape of grains, as well as on the amount and size of halite grains located in the intergranular space of sylvinites. The study of seams and mineralogical and petrographic studies of potash ore were carried out in order to determine the natural size of sylvinite grains, their shape, and the content of halite in the intergranular space.Moreover, the influence of these parameters on the beneficiation ability of the ore using dry cleaning process was determined. In addition, the data on laboratory studies using electric separation is provided in the paper. The results of the provided studies can be used by specialists of the mining industry when considering the influence of the mineral composition, size and shape of grains of potash ore in order to select the separation method at the early stages of development of potash deposits. The study of core material and mechanical properties, mineralogical and petrographic studies together with studies on beneficiation ability of ore presented in the article can be used, for example, in the preparation of a feasibility report.

Abstract: The article is devoted to the analysis of the internal structure and properties of a copper-graphite coating applied to a copper electrode. The article provides a calculation of the transient contact resistance of electrodes with a coating obtained using plasma spraying technology. Copper-graphite powder with high arc resistance was used as a spraying substance. Coated electrodes were tested for erosion resistance by an arc at currents of several kiloamperes. The aim of the work is to determine the effect of the composition and internal structure of the coating on the transient processes in the contact gap.

Abstract: Coloring silver for decorative purposes and for applying identification marks is an important task. In this paper, we consider a method for coloring silver surfaces using VIS plasmonic response in laser-induced nanoparticles (NPs). An analysis was made of the resulted morphology and chemical composition of nanoparticles obtained with nanosecond laser pulses. The dependence of the size and distribution of silver NPs on the laser exposure parameters is determined. The developed color palette was characterized using colorimetric coordinates.

Abstract: The detection of paraffin deposits in the systems of main oil pipelines today is a very important problem, since they lead to emergency oil spills, environmental disasters and economic losses both for the enterprise and for the country as a whole. This work is aimed at studying the physicochemical properties of asphaltic resin paraffins, as well as the mechanism of phase transition from liquid to crystalline. Such studies make it possible to estimate the absorption coefficient of the paraffin phase, which was previously not possible due to the complex nature of oil, consisting of hydrocarbons and many organic compounds of various molecular weights, and to provide high-precision non-contact measurements of the concentration of suspended asphalt-resin-paraffins in the oil flow in the pipeline. The analysis of the morphology and chemical composition of paraffins of various deposits is carried out, the dependence of the phase transition depending on the temperature gradient is determined.

Abstract: The need to develop new methods for predicting the properties of polymeric materials is also justified by the goal of designing new innovative materials with the required functional properties and increased competitiveness. The classical methods for predicting deformation processes of polymeric materials are based on the numerical solution of integral constitutive equations for polymer viscoelasticity of the Boltzmann-Volterra type, which do not consider corrections for the irreversibility of the plastic component of deformation and therefore can lead to significant prediction errors. To improve the accuracy of predicting the deformation processes of polymer materials it is proposed to introduce a physically justified correction with account for the irreversibility of the plastic component of deformation. The introduction of this correction significantly increases the reliability and accuracy of predicting the functional and operational properties of polymer materials. The article suggests demonstrating the methods for predicting deformation processes with the example of the polyester textile yarn made of polyester fibers. Unlike many other synthetic fibers, the polyester ones have such important properties as structural stability, softness along with high strength, elasticity, resilience, tensile strength, crease and pilling resistance, temperature regulation, shape retention, etc. The polyester fiber has a hollow structure and its single components have the form of spiral springs which give the effect of a springy base when intertwined.

Abstract: The article discusses the properties and features of heat-resistant titanium alloys. The microstructure of a new titanium alloy VT41, its mechanical and service properties after various processing modes are presented. The main problems in the machining of difficult-to-machine titanium alloys are considered. The developed mathematical model of the formation of errors in turning titanium alloys, taking into account thermal deformations and dimensional wear of the cutting tool, elastic deformations of the technological system, is described. The paper presents the results of experimental research on turning of heat-resistant titanium alloy VT41 on a multi-parameter stand.

Abstract: The concrete conglomerate properties change over time and depend on a number of factors. When considering deformation under the effect of mechanical loads or changes in temperature and humidity, the mechanism of this process is based on three main provisions. Firstly, concrete is a composite material, the matrix of which is cement stone. Secondly, the elastic modulus and strength of the cement stone may be less or more than that of aggregate. Thirdly, the concrete destruction under axial compression occurs at the cement stone stresses exceeding its ultimate extensibility in the direction normal to the external load action. Considering the specifics of deformation under load in different periods and the role of stress-related characteristics in this process, it is advisable to outline ways to regulate them and thereby the main concrete properties in the desired direction. The importance and feasibility of this approach are determined by the need to develop techniques allowing control of properties such as elasticity, shrinkage, and creep. A series of experimental tests and a comparative analysis of the results have been performed. The effect of some aggregate rocks on certain strength and stress-related properties of the concrete conglomerate has been investigated. Limestone and sandstone have been taken as the rocks studied. The properties studied include impact, axial compression, and axial tensile strengths. According to the analysis, concrete prepared on crushed limestone has shown the best results concerning all the properties studied.